20 H.P. Kohler swap please help!

[MWS LAWN]

I have a 99 model J.D. f-620 z-trak. It has a kohler CH20S engine on it. Does anyone know if a CH25S engine will match up and fit in the f-620. Are the blocks the same size, can I use the muffler off the old engine? I'm going to call Landscaper Supply tomorrow the difference in price of the two motors is only 80.00. Just wanting to know if anyone knows that it will work.

[Jman]

The blocks are all the same size. The mufflers are different. They will bolt up but the 25 muffler has less back pressure. The biggest thing to check is the size of the crankshaft, length and diameter.